The present invention relates to an apparatus for heating surfaces in the internal space of a motor vehicle.
Such an apparatus, with temperature acquisition associated with it, comprises at least one heating element having at least one heating conductor forming an electrical heating circuit, and at least one carrier material holding the heating conductor. The heating conductor has at least two heating conductor terminal ends (HC terminal ends) and the temperature acquisition element has at least two temperature acquisition element terminal ends (TA terminal ends).
Hereinafter, the abbreviation “HC”, refers to “heating conductor”, the abbreviation “TA” refers to “temperature acquisition” and “pcb” refers to “printed circuit board”.
Such apparatuses are used for heating surfaces in the internal space of motor vehicles, for example for heating steering wheels, seats, armrests, car mats, and ultimately for heating all possible surfaces within a motor vehicle that can be touched by a user.
Such apparatuses for heating usually have a temperature acquisition element in order to acquire the temperature in the heating area. As a consequence, such an apparatus for heating has terminal ends for the temperature acquisition element in addition to the terminal ends for the heating conductor. These connection parts must be designed such that they allow for a simple, easily accessible connection.
In the terminal area, wires serving as heating conductors or leads of the temperature acquisition device are twisted together or soldered together with the wires of the terminal leads and are insulated using heat shrink tubing, for example. In many cases these elements are also secured using glue and/or covers for strain relief. This process is laborious to carry out, and in particular the positioning of solder joints is, if possible at all, difficult to reproduce.
The objective of the present invention is to design a heating apparatus of the aforementioned kind such that the connection of the heating element with its connectors to the leads can be made reproducibly, and furthermore of providing the option of coupling the temperature acquisition element, thermally defined, to the heating conductor.
This objective is achieved, according to the present invention, by providing a heating apparatus wherein at least two of the HC and TA terminal ends are electrically connected to first HC terminal areas or first TA terminal areas of a printed circuit board and wherein the printed circuit board has second HC terminal areas and second TA terminal areas. The first HC terminal areas and the second HC terminal areas are, at least in part, connected to each other using first pcb traces and the first TA terminal areas and the second TA terminal areas are connected using second pcb traces, wherein the first and the second pcb traces are part of a printed circuit board, and wherein the printed circuit board is arranged on, under or at the carrier material.
Both the heating element and the temperature acquisition element are connected to electronics or an evaluation unit via the terminal areas arranged on the printed circuit board, i.e., the HC terminal areas (heating conductor terminal areas) and the TA terminal areas (temperature acquisition terminal areas). This process can be automated at least in part, especially since these terminal areas are located on the printed circuit board, which is preferably dimensioned very small. These terminal areas are pre-specified on the printed circuit board making it possible to reproduce and automate the processing steps.
For example, if the heating apparatus is provided for a steering wheel, the printed circuit board is positioned at a suitable area, for example at the steering wheel rim or the steering wheel hub. Prior to positioning and connecting the terminal ends for the heating conductor of the heating element (HC terminal ends) and the terminal ends for the temperature acquisition element (TA terminal ends) to the respective terminal areas located on the printed circuit board (first HC terminal areas and first TA terminal areas), the connections to the power supply for the heating conductor and the electrical connections to the temperature acquisition element and/or the connections to the electronics or evaluation unit are attached in preparation to the other ends of the pcb traces, i.e., to the second HC terminal areas and the second TA terminal areas. These attachments to the terminal areas can be carried out by soldering, crimping, welding or gluing, for example. An electrically conducting adhesive should be used for the aforementioned connection by gluing.
Such a printed circuit board is intended to be connected to parts of the steering wheel, for example, via a plug-type or also a clip-type connection. It is possible to dimension the printed circuit board in a sufficiently small design size such that it can be arranged in a steering wheel spoke of a steering wheel blank, and there preferably in an appropriately adapted recess. There, the terminal ends of the heating element or the heating conductor, respectively, and the terminal ends of the temperature acquisition element can be connected to the corresponding terminal areas of the pcb traces that are assigned to them.
The shape of the printed circuit board can be adapted to the circumstances by using a rectangular or a square shape. The corners can be rounded; however, an oval or trapezoidal shape in the top view of the printed circuit board is also provided.
The apparatus for heating with heating conductor and temperature acquisition element is particularly suited for heating small surface areas in the internal space of a motor vehicle, where only limited space is available for installing the connection elements that are associated with the heating conductor and the temperature acquisition element. In addition to heating a steering wheel, this apparatus is therefore also particularly well suited for heating a shift knob of a gearshift lever, an armrest or a grip handle. It is furthermore provided to employ such an apparatus for heating for trim components, for example of the door or the side sections of a motor vehicle, namely especially in areas where there is only limited space available for the connection components.
The printed circuit board has at least one first terminal area (first HC terminal area) that is associated with the terminal ends of the heating element's heating conductor, and at least one first terminal area (first TA terminal area) that is associated with the at least one first terminal ends of the temperature acquisition element. However, additional terminal areas can be provided as well that are associated with the additional terminal ends of the temperature acquisition element or the heating conductor.
Preferably, the one terminal areas, i.e., the first HC terminal areas and the first TA terminal areas, are arranged in the vicinity of an edge of the electrically insulating carrier material of the printed circuit board; the pcb traces then run preferably from this edge to the other terminal areas, i.e., the second HC terminal areas and the second TA terminal areas at the edge on the opposite side of the printed circuit board.
In one particularly preferred embodiment, the pcb trace(s) for the temperature acquisition element run(s) between the pcb traces for the heating conductor of the heating element.
Precisely in such an arrangement can the temperature acquisition element be connected directly to the two pcb traces that run between the pcb traces for the heating element, i.e., without additional wires between the temperature acquisition element and the terminal ends of the pcb traces. In particular, in such an arrangement, the heat emitted by the pcb traces of the heating element is detected by the temperature acquisition element and the temperature or the heating power of the heating element, respectively, is set dependant thereupon. When arranging the temperature acquisition element directly on the printed circuit board, it is possible to pre-populate the printed circuit board with a temperature acquisition element, for example as an SMD component (surface mounted device), and after installation of the apparatus for heating the temperature acquisition element will be reproducibly at an identical location in fixed association to the heating conductor or the heating element, or the pcb traces associated thereto, respectively, for the evaluation unit/electronics of the heating element.
It is also provided that the temperature acquisition element is in contact with a heat storing material in order to set the thermal inertia of the temperature acquisition element for the temperature control. Such heat storage can be arranged directly on the printed circuit board, for example by applying solder or through an SMD component on the printed circuit board.
The pcb trace(s) for the temperature acquisition element should be designed as web(s) with essentially equal widths, preferably as narrow pcb traces with a width of 0.2 mm to 1 mm each, even more preferred as narrow pcb traces with a width of 0.2 mm to 0.5 mm each. In contrast, the width of each pcb trace for the heating element or the heating conductor, respectively, is provided to be at least four times the width of a pcb trace for the temperature acquisition element. The maximum width of the pcb traces for the heating element should be in a range of 8 mm to 15 mm each. Preferably, the maximum width of the pcb traces for the heating element should be in a range of 8 mm to 10 mm each.
The conductor resistance of the respective pcb trace can be set via the shape and the trace route of the respective pcb trace on the printed circuit board and/or via the thickness of the pcb trace.
The preferred dimensions of the printed circuit board are 30 mm at most in each direction. Preferably, the dimensions vary from 10 mm to 30 mm. The printed circuit board can have a thickness of 0.3 mm to 5 mm; thin printed circuit board material should be used where thin, flexible heating elements or heating conductors, respectively are used and where adaptable and little thickening materials are required, for example at the steering wheel, while thicker materials for the printed circuit board should be used where mechanical stability and thus little warping has priority such as in a motor vehicle seat or in door panels. It is also provided to use a flexible printed circuit board where respective areas should adapt during installation.
To set the heat transfer through thermal conduction from the pcb traces that are correlated with the heating conductor, for example to a temperature acquisition element, which is also located on the printed circuit board, material of the carrier board is removed in the area of the temperature acquisition element between the respective pcb trace for the temperature acquisition element and the respective adjacent pcb trace for the heating element or the heating conductor, respectively, or the printed circuit board is provided with a penetration in this area. The thermal conductance from the pcb traces of the heating circuit to the temperature acquisition element can be set via the quantity of the material removed from the printed circuit board. A penetration of the carrier board, wherein such a penetration can also be referred to as an insection, should have a width of 0.3 to 3 mm, 1.5 to 2.5 mm, preferred of about 2 mm viewed in the plane of the carrier board. The thermal coupling can also be set via the material selection for the printed circuit board.
The connections of the terminal ends of the input leads and the connections of the heating conductor and the terminal ends of the temperature acquisition element with the respective associated terminal areas of the printed circuit board can be soldered, crimped, welded but also glued; the latter preferably using an electrically conducting adhesive. The thickness of the pcb trances, perpendicular to the plane of the printed circuit board is in a range of 30 μm-70 μm. As previously stated, the resistance of the pcb trace can be set via the shape and/or the route of the pcb trace. The resistance is decreased and thus the heat generation along the pcb trace of the heating conductor is reduced when using larger areas and greater thicknesses (greater cross-sectional areas). The pcb traces for the temperature acquisition element can be designed thin and narrow relative to the pcb traces of the heating circuit, for example with cross-sectional dimensions of 0.2 mm (material width)×30 μm (material thickness).
The thinner or narrower the pcb traces for the temperature acquisition element are designed, the fewer interferences will occur for the temperature acquisition element due the amount of heat generated across these pcb traces.
The invention can also be described as an apparatus with temperature acquisition for heating surfaces in the internal space of a motor vehicle having at least one heating element consisting of at least one heating circuit and one temperature acquisition element. The heating element has at least two terminal ends that can be connected to a power supply via connection lines. The temperature acquisition element has two contact ends, wherein at least one of these contact ends can be connected to electronics (evaluation electronics) via a connection lead. One respective pcb trace, which is part of a trace structure of an electrically insulating carrier board or printed circuit board, respectively, is located between the terminal ends and the respective associated terminal leads of the heating element and between the at least one contact end and the associated connection lead of the temperature acquisition element.
When reference is made in the description to the heating element, then this heating element also includes at least a carrier material to which a heating conductor is connected. This one heating conductor forms a heating circuit between its terminal ends. However, multiple heating conductors can also be arranged on the carrier material, wherein each of these heating conductors can form an autonomous heating circuit.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.